The present invention relates to current measuring systems employing a Faraday Effect current sensor.
Current sensors of this type are composed of a body of magneto-optic material provided with an opening through which extends a conductor carrying a current to be measured. The sensor further includes two polarizers which, together with the magneto-optic material, defines a light conduction path which extends around the conductor. Light radiation traversing this path experiences an intensity variation which is proportional to the instantaneous amplitude (positive or negative) of the current. Therefore, by comparing the intensities of the light radiation at the input and output of the light conduction path, it is possible to obtain a current measurement.
Typically, the light radiation is generated by a light-emitting element and received by a photodetector, each of which is coupled to one end of the light conducting path of the sensor by a respective fiber-optic cable. The light emitting element and the photodetector are electrically connected to form part of a suitable signal processing circuit.
While such a system is generally capable of providing a good current measurement, it is frequently desired to employ the system in environments in which the fiber-optic cables would be subjected to physical movements, such as shaking or vibrations, which will give rise, in the fiber-optic cables, to light intensity variations having frequency components comparable to the frequency of the current being monitored. Such intensity variations will significantly impair the accuracy of the current measurement.